1. Field of the Invention
The present invention relates to an illuminating element, more particularly to, an illuminating element with a dielectric optical long-wave multi-layer filter, hereinafter referred to as “wide AOI reflectance LPF”.
2. Description of the Related Art
With rapid advance of manufacturing, illuminating elements such as sun lamps, bulbs, and fluorescent lamps are largely applied to daily life. Nowadays how to enhance the illuminating efficiency and optical uniformity of illuminating elements is a major goal for research and development.
Refer to FIG. 1 as a sectional view of one of the conventional illuminating elements, and FIG. 1A is the locally zoomed view. As can be seen, the conventional illuminating element 100 comprises a transparent closed tube 110, mercurial gas (Hg) 120 and fluorescent film 130, wherein mercurial gas 120 is disposed within transparent closed tube 110, and a fluorescent film 130 is applied to the inner side 112 of the transparent closed tube 110. Additionally, said fluorescent film 130 is stacked by a plurality of dot-type fluorescent particles, and fluorescent film 130 can be further sectionalized to be top fluorescent film 132 and bottom fluorescent film 134.
After mercurial gas 120 is stimulated by high voltage, said mercurial gas 120 will emit ultraviolet light and illuminating on said fluorescent film 130, and the fluorescent particles 130a on said fluorescent film 130 will emit visible light after 130a is stimulated by ultraviolet light 122, and visible light 124 will pass through transparent closed tube 110 and illuminating all around.
However; the energy of the ultraviolet light 122 will decay as passing said fluorescent film 130, in such a way the fluorescent particles 130a′ at the top of the fluorescent film 132 and the fluorescent particle 130a″ at the bottom of fluorescent film 134 are stimulated in different scale. Thus, the fluorescent particle 130a′ and 130a″ will emit different-scale light as 124′, 124″ such that visible light 124″ is overall darker than visible light 124′.
Also, because said fluorescent film 130 is stacked by crystallized tiny fluorescent particle 130a, more or less ultraviolet light will permeate through the tiny apertures between fluorescent particles 130a therefore some waste will be introduced and energy efficiency will be reduced.
In addition, as said fluorescent film 130 is not a fine transparent body, visible light emitted from said fluorescent particle 130a′ must permeate through bottom fluorescent film 134, in order to illuminate outside. In this way the brightness of visible light 124′ will be reduced. Therefore, if we can adjust the thickness of fluorescent film 130 and said ultraviolet light 122 is amply absorbed, and the illumination efficiency can be enhanced.
FIG. 1B is another locally zoomed view of another conventional illuminating element. Please refer to FIG. 1B and FIG. 1A. A illuminating element 100a in FIG. 1B and a illuminating element 100 in FIG. 1A are ditto but their difference is the thickness of the fluorescent film 130′ of the illuminating element 100a is less than that of the fluorescent film 130 of illuminating element 100. While coating for fluorescent film 130′, due to the thinner fluorescent film 130′, the transparency will be enhanced but it will also suffer from the incomplete stacking and some areas are not fully covered.
Correspondingly, a large portion of the ultraviolet light 122′ will directly punch through fluorescent film 130 to be wasted and leads to inferior brightness. If at this time the wasted ultraviolet light can be reflected for utilization, then the better pervious to light (fluorescent film 130′) and better utilization allow the illuminating efficiency to be greatly improved.
FIG. 2 is another sectional view of conventional illuminating element. In FIG. 2 a conventional illuminating element 200 comprises transparent closed tube 210, mercurial gas 220, fluorescent film 230 and reflecting film 240, wherein mercurial gas 220 is disposed in transparent closed tube 210. The transparent closed tube 210 is partitioned to a bottom inner side 212 and an upper inner side 214. The reflecting film 240 is coated on said bottom inner side 212 and fluorescent film 230 is coated on the reflecting film 240.
While mercurial gas 220 emitting ultraviolet light 222(222′) and illuminating on fluorescent film 230, 230 will be stimulated to emit visible light 224. A part of visible light 224′ can directly pass through said upper inner side 214 and the transparent closed tube 210 to shine the outside, and some other part of visible light 224″ will be reflected by the reflecting film 240 and pass through the transparent closed tube 210.
Despite the major illuminating by the surface of fluorescent 230 for the illuminating element 200, some part of visible light 224′ can directly illuminate the external world without passing through the fluorescent film 230 such that the entire brightness of the illuminating element 200 is slightly enhanced. However; due to the semicircle coating of fluorescent film 230, some upward ultraviolet 222″ cannot illuminate the fluorescent film 230 for radiating and this situation caused the energy lose and reduced the energy valid efficiency for the illuminating element 200.